1. Field of the Invention
This invention relates to an equipment for discharging treated articles, automatically, easily and completely, from a barrel which contains the articles during surface treatments, such as galvanizing, coating and etching, in a surface treatment system.
2. Description of the Prior Art
For galvanizing, for example, metal articles in an automatic plating apparatus, the articles undergo a cycle of predetermined treatments in the order of pre-treatments, galvanization and after-treatment. For this purpose, a processing line is prepared by arranging liquid-containing tanks in a desired order. Relatively large articles to be surface-treated are hung from a transporter which moves along a rail extending above the processing line. At a point during the movement, the transporter is lowered to immerse the article in a treatment liquid in a tank for one of the desired surface treatments, and it is moved up to remove the article from the treatment liquid. Then the transporter runs to a next point for a next treatment by a next treatment liquid.
Relatively small articles to be treated are held in a cylindrical porous container, called "barrel", which is hung from the transporter, throughout the entire cycle of predetermined treatments. After a final treatment, the articles are discharged from the barrel, and the barrel is sent to a next cycle of the same treatments after charged with new pre-treated articles. The barrel has an aperture in its peripheral wall normally closed by a cover, so that articles are charged or discharged through the aperture.
It is sometimes difficult to discharge the full amount of treated articles from the barrel. In case of cubic, spherical or rod-shaped articles contact whose contacting areas with the barrel are relatively small, it is not difficult to discharge the full amount of such articles even if they are light-weight. However, light-weight flat-shaped articles, which may contact with the barrel with large flat areas, are apt to cling or stick to inner surfaces of the barrel. Once the articles cling to the barrel, it is difficult to remove them from the barrel even by applying vibrations, because a surface tension of a treatment liquid film existing between the articles and the inner surface of the barrel holds the articles on the barrel wall.
If the treated articles remain in the barrel, they are again sent to a next processing cycle together with newly charged pre-treated articles. As a result, the next discharged cargo will contain double-treated defective articles. Therefore, the reliability on the products or the yield of products is decreased.
It is certainly very difficult to remove articles clinging to the barrel with a surface tension of a liquid film. Scraping and repeated application of an impulse to the barrel may be effective to a certain extent; however, it is troublesome to scrape out such articles by inserting a tool to the interior of the barrel, and strong impulse may damage treated products.
A prior art disclosed in Japanese Patent Kokai Publication No. Sho 61-194199 proposes to remove articles from a barrel wall by using a jet stream of water sprayed out through a nozzle into the barrel held in the air. However, much energy is required to provide an effectively strong jet of water, and it takes much time to remove such articles from the barrel. Moreover, despite such efforts, some of the articles may still remain on the barrel wall.